Cleanup code using forward declarations.

Use misc methods of avoiding unnecesary header includes.
Replace int typedefs with int##_t from stdint.h.
Replace PRI64[xdu] with PRI[xdu]64 from inttypes.h.
Normalize QT_VERSION ifs where possible.
Resolve some indirect dependencies as direct ones.
Remove extern declarations from .cpp files.

src/test/base64_tests.cpp

@@ -1,9 +1,9 @@
-#include <boost/test/unit_test.hpp>
 
-#include "main.h"
-#include "wallet.h"
+
 #include "util.h"
 
+#include <boost/test/unit_test.hpp>
+
 BOOST_AUTO_TEST_SUITE(base64_tests)
 
 BOOST_AUTO_TEST_CASE(base64_testvectors)